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Adult frogs do not have tails and caecilians have only very short ones. [69] Didactic model of an amphibian heart. Salamanders use their tails in defence and some are prepared to jettison them to save their lives in a process known as autotomy. Certain species in the Plethodontidae have a weak zone at the base of the tail and use this strategy ...
Feather variations. Feathers are epidermal growths that form a distinctive outer covering, or plumage, on both avian (bird) and some non-avian dinosaurs and other archosaurs. They are the most complex integumentary structures found in vertebrates [1] [2] and an example of a complex evolutionary novelty. [3]
The calamus is hollow and has pith formed from the dry remains of the feather pulp, and the calamus opens below by an inferior umbilicus and above by a superior umbilicus. [2] The stalk above the calamus is a solid rachis having an umbilical groove on its underside. Pennaceous feathers have a rachis with vanes or vaxillum spreading to either side.
The scales and scutes of birds were thought to be homologous to those of reptiles, [4] but are now agreed to have evolved independently, being degenerate feathers. [5] [6] Carcharodontosaurid theropod dinosaur Concavenator, is known to have possessed these feather-derived tarsal scutes.
After internal fertilization and the habit of laying eggs in terrestrial environments became a reproduction strategy amongst the amniote ancestors, the next major breakthrough appears to have involved a gradual replacement of the gelatinous coating covering the amphibian egg with a fibrous shell membrane. This allowed the egg to increase both ...
In Australia, many mammals (and all mammalian gliders) possess, to some extent, prehensile tails. Globally, smaller gliding species tend to have feather-like tails and larger species have fur covered round bushy tails, [10] but smaller animals tend to rely on parachuting rather than developing gliding membranes. [9]
Male blue tits have an ultraviolet reflective crown patch which is displayed in courtship by posturing and raising of their nape feathers. [119] Ultraviolet light is also used in foraging— kestrels have been shown to search for prey by detecting the UV reflective urine trail marks left on the ground by rodents. [ 120 ]
Caecilians have small or absent eyes, with only a single known class of photoreceptors, and their vision is limited to dark-light perception. [17] [18] Unlike other modern amphibians (frogs and salamanders) the skull is compact and solid, with few large openings between plate-like cranial bones. The snout is pointed and bullet-shaped, used to ...